An explosion struck near a patrol of the U.S.-led coalition in the northern Syrian town of Manbij, killing and wounding more than a dozen people, a Syrian war monitoring group and a local town council said. The Britain-based Syrian Observatory for Human Rights said 16 people were killed including nine civilians and others were wounded in the blast. It added that at least five U.S.-backed Syrian fighters were also among the dead.

A mysterious gray Sikorsky S-92 helicopter linked to U.S. special operations forces in the region swooped in afterward to evacuate casualties. All of this comes as the United States moves ahead with plans to withdraw from the country entirely.

Footage shows US helicopter taking off from #Manbij municipal football court. Helicopter had landed near blast site. US casualties reported. pic.twitter.com/mf6srNOV24

“U.S. service members were killed during an explosion while conducting a routine patrol in Syria today. We are still gathering information and will share additional details at a later time,” the tweet said.

The coalition has not said how many service members were killed.

CAUTION, the video below may be disturbing to some viewers:

Footage of the #Manbij explosion. It looks like it might have been a suicide bomber. Seems as if someone pulls on a detonator just before the explosion. pic.twitter.com/285RbeNzT7

The attack occurred around 12:40 PM local time on Jan. 16, 2019 on a busy street in Manbij near a market. Unconfirmed reports from the U.S.-backed Manbij Military Council and the U.K.-based Syrian Observatory for Human Rights say that there may be more than two dozen dead and wounded, including up to four American troops.

After the attack, witnesses on the ground also spotted a gray S-92 helicopter arriving to evacuate casualties. This chopper is similar if not identical to one that has previously appeared in areas where U.S. forces and their local partners operate in Syria and was traced back to a U.S. based contractor. You can read more about this unique aircraft and its shadowy origins here.

Confirmed: At least 4 US soldiers were here where the explosion took place.